The field of the invention is integrated circuit processing, including circuits having resistors.
When a circuit requires a resistor, conventional processing uses a strip of polysilicon or an implanted area in the substrate, the dimensions and amount of doping being set to give the desired resistance. Both these approaches are planar and require substantial chip area, as well as additional processing steps to give a resistivity that is different from the resistivity of poly interconnect or sources and drains.
As IC dimensions shrink, the extra area required for a planar resistor becomes more of a burden.
The invention relates to a method of forming vertical resistors that employs steps that are used for forming a deep trench capacitor in a DRAM.
A feature of the invention is the use of a germanium liner in a deep trench that can be selectively removed to isolate a vertical resistive element placed in the trench from the substrate, while still making ohmic contact with the substrate at the bottom of the trench.